1. Field of the Invention
This invention relates to optical fiber expanded beam connectors and, in particular, to an integral lensing and alignment device for an optical fiber. The invention is further directed to a multi-piece mold for such a device, and to a generally truncated conical elastomeric washer for holding and centering an optical fiber. Furthermore, the invention is also directed to a fiber optic expanded beam connector assembly. Accordingly, it is a general object of this invention to provide new and improved devices, molds, washers and assemblies of such character.
2. General Background
The coupling of two optical fibers to achieve maximum transmission of light between them may be accomplished by a direct end to end alignment or by use of intermediate focusing optics. In the latter approach, the light wave is expanded in cross-section so that it is possible to relax the transverse alignment accuracy requirement and also to have a connector that is less susceptible to contamination upon repeated connections and disconnections. U.S. Pat. No. 4,421,383 by W. John Carlsen, issued Dec. 20, 1983, entitled "Optical Fiber Connectors", describes such an optical fiber connector in which the convex lens surface, a forward flat reference surface, and a focal plane surface are integrally molded in an optical quality plastic component. Transverse location of the fiber end at the focal point on the focal plane is achieved by means of an elastomeric centering device as described in U.S. Pat. No. 4,391,487 by Paul Melman and W. John Carlsen, issued July 5, 1983 and entitled "Optical Fiber Centering Device". This centering device utilizes a cylindrical recess in a transparent plastic component. Additional final alignment can be achieved through the use of a truncated conical indentation to further center the end of the fiber, as described in Optical Spectra, October 1980, pp. 41, 42, article entitled "Connectors at Stretch" by Carlsen and Melman.
The outer surface of the optical plastic connector body part, as shown in the aforesaid Carlsen patent, U.S. Pat. No. 4,421,383, is essentially cylindrical with the addition of configurations for holding a pair of such components in an expanded beam connector. Such configurations can include, for example, chamfers, raised rings or other types of flanges. Disadvantageously, however, such cylindrical surfaces complicate the design of a mold necessary for forming the optical quality transparent material, such as plastic or glass, into shape. Further, to mold an internal cylindrical recess with a fiber location detent at its bottom would require a die insert pin having a conical point on its end to reproduce such a detent. To maintain the exact location of such a detent relative to the other parts of the die that form the forward reference plane and recessed convex lens surface under molding conditions is difficult because such an insert pin may deform. Further, the opening and the reassembling of a die between molding operations require high precision to achieve the desired focal alignment.